Slashdot Mirror
Simulating the Universe with a zBox
An anonymous reader writes "Scientists at the University of Zurich predict that our galaxy is filled with a quadrillion clouds of dark matter with the mass of the Earth and size of the
solar system. The results in this weeks journal Nature, also covered in Astronomy magazine, were made using a six month calculation on hundreds of processors of a self-built supercomputer, the zBox. This novel machine is a high density cube of processors cooled by a central airflow system. I like the initial back of an envelope design. Apparently, one of these ghostly dark matter haloes passes through the solar system every few thousand years leaving a trail of high energy gamma ray photons."
At the center of the box is a small piece of fairy cake
zBox has been slashdotted, vat do ve do now? Ve relax and eat some cheese and chocolate, jawohl!
...you just slashdotted Switzerland. Who's next, tough guy? Andorra?
Chip H.
You can read the entire paper in PDF or PS at astro-ph, a web site which collects preprints in the physical sciences. See
http://xxx.lanl.gov/abs/astro-ph/0501589
I read the paper quickly. The authors have to come up with a model which has virtually no observable consequences (otherwise, we would have seen this source of matter by now), but which can also be tested experimentally in the not-too-distant-future (or else it wouldn't be science). They predict that some of the cosmic-ray shower telescopes may be able to detect the little cloudlets of dark matter. We'll see.
Michael Richmond "This is the heart that broke my finger."
mwrsps@rit.edu http://stupendous.rit.edu
Maybe they should have use the zbox to host their site =)
i k.unizh.ch/~stadel/zBox/
http://rufus.hackish.org/~rufus/mirror/krone.phys
All it keeps saying is 42...42...42...42...
You can legislate morally you can't legislate morality
The problem in question is the number of distinguishable bodies. With weather you would have to go down to the single molecule in the air, to get a quite good prediction. In fact current weather models use cubes of air where the conditions are considered constant (same temperature, same pressure, same direction of air flow in the same cube) and take them as distinguishable bodies. Those models are a compromise between the sheer number of necessary elements, the number crunching limits of current calculation hardware and the difference between the used model and the reality.
With stellar bodies it's much more easy. The number of stellar bodies you need for a prediction is much smaller, the bodies themself can be considered almost constant for the whole calculation etc.pp. With the number crunching capacity of today's weather prediction centers you can simulate whole galaxies (if you consider stars constant, which they mainly are for about 10mio to 10bio years, depending on their mass). With the differences between your model and the measured reality you can spot elements you didn't simulate yet and add them to your model. The swiss team now was simulating clouds of about the mass of the earth and the size of the solar system and found that those added to the stellar simulation made a quite good fit to the measured data.
It'd be interesting if these things could be tied to mass extinctions, but these occur much more rarely than every few thousand years. And unless these clouds can account for high levels of iridium, shocked quartz, melt glass, and a hundred-mile impact crater in Mexico, it's not terribly likely they account for the dinosaur extinction.
The reason I'm interested is that a non-neutral charge distribution would tend to attract the outer part of the galaxy towards the centre more than would be expected from gravity alone, which is (simplistically) the evidence for dark matter / energy.
If the computer ran for 6 months straight using 1.8GHz processors, couldn't they have waited several months and utilized newer CPUs running at double the speed, halving the computation time?
Regarding their design, I'm somewhat surprised they used an individual power supply for each board. It seems there would be more efficient and smaller power systems available that could power multiple boards at once. It looks like a quarter of the volume of the computer is comprised of power supplies. Plus all that extra heat is thrown into the mix too.
Dan East
Better known as 318230.
a self-built supercomputer
I thought we where years away from having to defend ourselves against the machines...